On the impact of imperfect models for multiple VLBI antennas on the Genesis satellite on the terrestrial reference frame

The European Space Agency’s (ESA) Genesis mission has been approved for launch in 2028. Its primary objective is to enhance the terrestrial reference frame by establishing a space tie on board the Genesis satellite that connects all space-geodetic techniques used for its realization.

Concerning the VLBI part of Genesis, new challenges arise from the fact that the VLBI broadband signal will be spread across multiple antennas on the satellite, each emitting in its own bandwidth. If this aspect is not corrected for with sufficient accuracy, the group delays will not refer to a well-defined reference point on the satellite.

In this study, we investigate how large the impact of neglecting such a correction or imperfectly modelling it would be on estimated parameters, such as station positions. We address this question by simulating observations to the Genesis satellite on the group delay level. Based on simulated 24-hour sessions, consisting of quasar and satellite observations, a full geodetic VLBI analysis is carried out, using the software VieVS-VLBI. Here we present our results and discuss the necessity of phase center corrections for VLBI observations to the Genesis satellite.